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Embracing mixed oxide state response course, lead-free polycrystalline 0.075(K0.5Bi0.5TiO3)–0.925 (NaNbO3) or 0.075 (KBT)–0.925 (NN) ceramic integrate, and its optical, auxiliary, dielectric, ferroelectric, and impedance properties are investigated. Basic examination represents the arrangement of new perovskite, with an orthorhombic structure having space bunch as Pmc21. FESEM micrograph proves the closeness of homogeneous nature in morphology. FTIR analysis suggests that there is a change in the vibrational mode of phonons due to the inclusion of NN with KBT. The optical band gap of the material is 3.06 eV as obtained from the diffuse absorbance spectra which is suitable for the photo-catalytic application. From Raman spectra, it is seen quite different vibrational modes from 130 to 900 cm−1. Polarization study affirms the ferroelectric idea of the present investigation. Dielectric and complex impedance investigations are carried out in the frequency range of 102–106 Hz and temperature range of 30–500 °C. AC conductivity range is represented by Jonscher's power law. AC conductivity reveals the semiconducting nature of the material. [ABSTRACT FROM AUTHOR]

In this research article, we report the various functional properties of [Pb(Fe0.5Nb0.5)O3]0.2- [(Ca0.2Sr0.8)TiO3]0.8 perovskite ceramic compound prepared by the solid-state process. Rietveld refinement proved that the compound crystallises in a pseudocubic structure as the primary phase. The dual oxidation states of Fe, Nb, Ti and the presence of oxygen vacancies were analysed by X-ray photoelectron spectroscopy. Ti–O and Ti–O–Ti prominent perovskite vibrations were examined by Fourier transform infrared (FTIR) analysis. Raman spectroscopy technique was employed to study the asymmetric TiO6 octahedral stretching and A1g phonon mode of PbFe0.5Nb0.5O3 (PFN). Field emission scanning electron microscopy (FESEM) predicted better grain growth with an average grain size of 2.445 µm. Energy-dispersive X-ray spectroscopy (EDS) analysis was done for elemental confirmation and purity of the sample. A detailed optical analysis was done by incorporating both absorbance and diffuse reflectance spectroscopy. A narrow band gap was revealed from the optical studies and Urbach energy was analysed. The conduction band minimum (CBM) level was estimated to be − 1.14 eV exploring the photocatalytic response. Electrical properties were investigated in terms of dielectric constant, conductivity, complex impedance and modulus analyses. A weak ferroelectric response was noticed with the remnant polarisation of 0.181 µC / cm2 from P–E loop analysis. Mössbauer spectroscopy revealed a strong paramagnetic doublet indicating the high-spin Fe3+ species in the octahedral environment. [ABSTRACT FROM AUTHOR]

In this research article, we report the various functional properties of [Pb(Fe0.5Nb0.5)O3]0.2- [(Ca0.2Sr0.8)TiO3]0.8 perovskite ceramic compound prepared by the solid-state process. Rietveld refinement proved that the compound crystallises in a pseudocubic structure as the primary phase. The dual oxidation states of Fe, Nb, Ti and the presence of oxygen vacancies were analysed by X-ray photoelectron spectroscopy. Ti–O and Ti–O–Ti prominent perovskite vibrations were examined by Fourier transform infrared (FTIR) analysis. Raman spectroscopy technique was employed to study the asymmetric TiO6 octahedral stretching and A1g phonon mode of PbFe0.5Nb0.5O3 (PFN). Field emission scanning electron microscopy (FESEM) predicted better grain growth with an average grain size of 2.445 µm. Energy-dispersive X-ray spectroscopy (EDS) analysis was done for elemental confirmation and purity of the sample. A detailed optical analysis was done by incorporating both absorbance and diffuse reflectance spectroscopy. A narrow band gap was revealed from the optical studies and Urbach energy was analysed. The conduction band minimum (CBM) level was estimated to be − 1.14 eV exploring the photocatalytic response. Electrical properties were investigated in terms of dielectric constant, conductivity, complex impedance and modulus analyses. A weak ferroelectric response was noticed with the remnant polarisation of 0.181 µC / cm2 from P–E loop analysis. Mössbauer spectroscopy revealed a strong paramagnetic doublet indicating the high-spin Fe3+ species in the octahedral environment. [ABSTRACT FROM AUTHOR]

A polycrystalline sample of ([Bi.sub.0.5][K.sub.0.5])([Fe.sub.0.5][Nb.sub.0.5])[O.sub.3] was prepared using a mixed oxide at 1000°C. The preliminary structural analysis using X-ray diffraction data of the compound indicates the formation of a single-phase rhombohedral structure similar to that of parent BiFe[O.sub.3]. Microstructural and elemental analysis using a scanning electron micrograph and energy-dispersive X-ray spectroscopy, respectively, were carried out at room temperature with higher magnification exhibiting a uniform distribution of grains and stoichiometry. The appearance of hysteresis loops (P-E) confirms the existence of ferroelectricity of the sample with a high remnant polarization of (2[P.sub.r]) 17.76 µC [cm.sup.-2]. Using impedance spectroscopy, the electrical properties of the material were investigated at a wide range of temperature (25-500°C) and frequencies (1 kHz-1 MHz) suggesting dielectric non-Debye-type relaxation in the material. The nature of the Nyquist plot (Z' ~ Z') shows the dominance of the grain contribution in the impedance. The bulk resistance of the compound decreases with increasing temperature, like that of a semiconductor, which shows a negative temperature coefficient of resistance (NTCR) behavior. The frequency dependence of AC conductivity suggests that that the material obeys Jonscher's power law. Magnetic hysteresis (M-H) loop shows very weak ferromagnetic behavior at room temperature. PACS Nos.: 75.85+t, 61.10.Nz, 77.22.-d, 72.80.Le. Nous preparons un echantillon poly-cristallin de ([Bi.sub.0.5][K.sub.0.5])([Fe.sub.0.5][Nb.sub.0.5])[O.sub.3] par melange d'oxydes a 1000°C. L'analyse preliminaire de structure a l'aide de la diffraction X indique la formation d'une structure rhomboedre a phase unique, similaire a celle du parent BiFe[O.sub.3]. L'analyse micro-structurelle et fondamentale utilisant les techniques SEM et EDAX de micrographie electronique a balayage, a la temperature de la piece et plus haute magnification, montre une distribution uniforme des grains et de la strechiometrie. L'apparition de boucles d'hysterese (P-E) confirme la ferroelectricite de l'echantillon avec une haute polarisation remanente de (2[P.sub.r]) 17.76 µC [cm.sup.-2]. L'utilisation d'une technique de spectroscopie d'impedance permet une etude des proprietes electriques de l'echantillon, sur de larges domaines de temperature (25-500°C) et de frequence (1 kHz-1 MHz), qui suggere une relaxation dielectrique dans le materiel qui n'est pas du type Debye. Le graphique (Z' ~ Z') de Nyquist montre la dominance de la domination du grain dans l'impedance. La resistance en volume de l'echantillon decroit lorsqu'augmente la temperature, de faxon similaire a un semi-conducteur avec un coefficient thermique de resistance negatif. La dependance en frequence de la conductivite ac suggere que le materiel obeit a une loi de puissance de Joncher. La boucle d'hysterese (M-H) est caracteristique d'un tres faible ferromagnetisme a la temperature de la piece. [Traduit par le Redaction], 1. Introduction Multiferroics exhibit multiple ferroic properties (i.e., ferroelectricity and ferromagnetism in a structurally distorted system), which allow mutual control of electric polarization with magnetic field or controlling magnetization by [...]

In this study, the impact of Nd doping on the structural, microstructural, dielectric, ferroelectric, and transport properties of Pb (1 - x) Nd x (Fe 0.5 Nb 0.5) 1 - x / 4 O 3 (PNFN) solid solutions ( x = 0 , 0.02 , 0.04 , 0.08 , and 0.1 ) is reported. For all the solid solutions, room temperature Rietveld refined X-ray diffraction (XRD) analysis reveals the monoclinic crystal structure with Cm space group. From Field emission scanning electron microscope (FESEM) studies, the polyhedral-shaped grains are found to be homogeneously distributed. Variation of dielectric properties with temperature displays the decrease of phase transition temperature (TC) with increasing Nd content. The temperature-dependent AC conductivity follows the Arrhenius behavior and the activation energies are calculated for high temperature regions. The frequency dependent AC conductivity behavior obeys the Johnscher's power law. Impedance spectroscopy results show the impact of conductivity from the bulk (grain) and displays non-Debye type of behaviour. Electric modulus demonstrates thermally activated relaxation phenomenon in the materials. Polarization vs. electric field (P-E) loops analysis confirms the ferroelectric nature of the materials. With increase in Nd concentrations, the value of remanent polarization (2Pr) increases, on the other hand, the coercive field (2Ec) value decreases. Both of these properties are suitable for enhancement of the physical properties of the multiferroic materials. [ABSTRACT FROM AUTHOR]

Samarium-modified BiFe[O.sub.3] (i.e., [Bi.sub.1-x][Sm.sub.x]Fe[O.sub.3] (BSFO); x = 0, 0.1, and 0.2) ceramics were synthesized using a solid-state reaction method. Preliminary X-ray structural analysis shows that BSFO polycrystalline compounds have rhombohedral crystal structure. These samples showed dispersion in permittivity ([[epsilon].sub.r]) and dielectric loss (tan[delta]) at lower frequencies. The scanning electron micrographs of the compounds showed (i) the uniform distribution of grains on the samples' surface with high density and (ii) reduction of grain size on Sm-substitution at the Bi site of BiFe[O.sub.3]. The materials exhibit temperature dependence of dielectric relaxation phenomena. Study of temperature dependence of dc conductivity of the materials follows Arrhenius behavior. The ac conductivity of BSFO obeys Jonscher's universal power law. Studies of impedance and its related parameters of the materials exhibit a strong correlation between its microstructure (i.e., bulk, grain boundary, etc.), electrical and magnetic parameters. PACS Nos.: 75.85. +t, 77.80.-e, 72.80.Le, 75.50.-y. Utilisant une reaction a l'etat solide, nous synthetisons des ceramiques BiFe[O.sub.3] modifiees au samarium (du B[i.sub.1-x]S[m.sub.x]Fe[O.sub.3] (BSFO) ; x = 0, 0.1, 0.2). Une etude preliminaire par rayon X montre que le compose poly-cristallin de BSFO a une structure cristalline rhomboedrique. Ces echantillons montrent une dispersion en permittivite ([[epsilon].sub.r]) et une perte dielectrique (tan[delta]) aux frequences plus basses. Le micrographe electronique montre (i) une distribution uniforme des grains sur la surface de l'echantillon avec une haute densite et (ii) une reduction de la grosseur des grains sur l'echantillon lors d'une substitution Sm. Les phenomenes de relaxation dielectrique de ce materiau dependent de la temperature. La dependance en temperature de la conductivite dc suit la loi d'Arrhenius. La conductivite ac du BSFO obeit a la loi de puissance universelle de Jonscher. L'etude de l'impedance et des parametres associes montre une forte correlation entre la microstructure (comme en volume, bordure de grain, etc.) et les parametres magnetiques et electriques. [Traduit par la Redaction], 1. Introduction Multiferroic materials are technologically and scientifically important because of their potential applications in information storage, multiple-state memories, magnetic data-storage media, actuators, transducers, sensors, quantum electromagnets, microelectronic devices, and [...]